Maintenance Dredging Gladstone

Port of Gladstone

The main navigational shipping infrastructure within the Port of Gladstone typically requires annual maintenance dredging. Maintenance dredging of additional facilities such as the Gladstone Marina is undertaken when required.

The purpose of this Long-term Maintenance Dredging Management Plan (LMDMP) is to address operational needs, environmental risks, monitoring and adaptive management actions specific to the Port of Gladstone whilst ensuring the ongoing sustainability of maintenance dredging within the port.

Framework

• Port of Gladstone – Long-term Maintenance Dredging Management Plan
• Maintenance Dredging Environmental Management Plan
• Maintenance Dredging Environmental Monitoring Procedure
• Risk Assessment for Scheduling Maintenance Dredging
• Port of Gladstone Marina Maintenance Dredging Environmental Management Plan
• Port of Gladstone Marina Maintenance Dredging Environmental Monitoring Procedure

A range of studies relevant to maintenance dredging informed the preparation of our LMDMP and the development of its associated management documents. The LMDMP commits to the availability of a range of these documents. These include the outcomes of programs in the long-term maintenance dredging monitoring schedule. This information will be updated and revised periodically considering recent investigations in response to changes in risk, or as a result of the completion of monitoring as per the long-term maintenance dredging schedule.

Latest monitoring reports

• Sediment Quality Plan
• Sediment Quality Implementation Report
• Water Quality Real Time Impact Detection
• Water Quality Sediment Investigations
• Water Quality Bioavailability Study
• Water Quality (Potential Impacts Assessment)
• Water Quality (Plume Validation Study)
• Sensitive Receptors BPAR Real Time
• Sensitive Receptors Reef Conditions Survey
• Benthic Habitats and Communities Survey
• Hydrographic Survey
• Marine Pest Survey
• Ambient Survey Water Quality — Gladstone Healthy Harbour Partnership and Port Curtis Integrated Monitoring Program
• Ambient Survey (Coastal Seagrass)
• Surveys of the Reef Communities of Facing Island 2023

Latest regulatory reports

• Sea Dumping Permit International Reporting
• Water Quality Environmental Compliance Report
• Water Quality Environment Compliance Report (Marina)

Technical Advisory and Consultative Committee

The Technical Advisory and Consultative Committee (TACC) provides a forum to understand our maintenance dredging activities and to assist GPC and regulatory agencies with accessing local knowledge and reconciling stakeholder interests.

Monitoring

What is turbidity?
Turbidity is a measure of water clarity.

The turbidity is the cloudiness or haziness of the fluid which is caused by suspended particles.

What is BPAR?
Benthic photosynthetically (BPAR) is active radiation, a measure of the amount of light that reaches the sea floor. BPAR can be affected by factors in the air (cloud cover) or in the water (turbidity).

What do the colour icons mean?
GPC monitors two types of water quality aspects throughout the Maintenance Dredging project —turbidity and BPAR (light). These water quality measures are displayed on the live map below.

If the turbidity level is below the 95th percentile at a site, it is represented by a green (level 1) circle icon. If the turbidity level is above the 95th percentile at a site, it is represented by an orange (level 2) circle icon.

BPAR (light) is the opposite, whereby a higher value is a better result. If the BPAR (light) level is above the minimum light threshold at a site, it is represented by a green (level 1) circle icon. If the BPAR (light) level is below the minimum threshold at a site, it is represented by an orange (level 2) circle icon.

Orange does not necessarily mean bad, just that the turbidity or light levels are reaching levels that are higher than average conditions. While dredging can impact turbidity and in turn light levels in the harbour, based on the two baseline campaigns undertaken for this project (together spanning more than eighteen months) it is expected the most significant and frequent changes in turbidity and light will be driven by natural environmental factors.

These factors are typical of estuaries such as Port Curtis, as a result of spring tides, rainfall events/storms, high winds and large swell events.

How is the monitoring data used?
Monitoring stations located throughout Port Curtis provide real time data to a dedicated team of experts at GPC, as well as third parties for additional technical support.

The team will monitor conditions and modify dredging operations as required to ensure turbidity caused by dredging does not impact on light levels.

What is a trigger?
A trigger is the threshold or percentile intensity of a site. For example:

Turbidity Level 2 is reached when turbidity values increase above the 95th percentile or ‘trigger’ for more than 24 consecutive hours.

BPAR (Light) Level 2 is reached when values decrease below the threshold or ‘trigger’ for seven consecutive days, indicating less light is available in the water column to reach seagrass.

If a trigger is reached, GPC will initiate an investigation to determine the likely cause and will notify regulators. If elevated or decreased levels are found to be caused by dredging, GPC will work with the dredging contractor to modify operations such as speeds or location.

Note: Specifically in the case of light, if reduced light conditions persist for 14 consecutive days and the investigation determines that dredging activities are the cause, GPC will cease dredging operations until light values return above the trigger for 24 hours. In this instance turbidity is expected to be elevated as dredging activates cannot directly affect light levels without a significant increase in turbidity.

Click HERE to display the live map for water quality measures.